Cinematograph positive film



, J. E. THORNTON Jan. 29, 1929.

Filed Jue 14, 1924 Patented Jan. 29, 1929.

UNITED STA JOHN EDWARD THORNTON, OF LONDON, ENGLAND.

CINEMATOGRAPVH POSITIVE IFILM.

Application filed .Tune 14, 1924, Serial No. 720,127, and in Great Britain October 19, 1928.

This'invention relates to improvements in lthe production of cinematograph film posi-- l 'tives of monochrome pictures as distinct from multi-color pictures.

In the. specifications of my applications Serial Nos. 680,511, filed December 13, 1923, and 711,251 led May 5, 1924, I have described' a positive cinematograph film in multi-colors built up of two thin. films cemented together face-to-face to render the pictures thereon scratcliless and immune from damage.

The object of this invention is the production of scratchless enclosed cinematogra-ph film-prints in one color only (generally described as monochrome), and can be used for building up such monochrome film-prints of any of the following types (A) Pictures in one single color, generally termed monochrome, but formed upon only one of the two thin film-sections.

(B) Pictures in one single color, formed by printing identical images from the same negative upon both sections of the film, but with one of the prints reversed in relation to the other, so that when united both sections of the same image will reinforce each other and will superimpose to form only one complete image. l

(C) Double-tone monochrome pictures, in which those printed upon one section-film will emphasize the lighter tones of the picture and those upon the other section-film will emphasize the darker tones or shadows of the picture. In this way' prints with great beauty of tone and very long scale of gradationcan be produced, each being in different shades of the same color, or both in u'the same shade of the same color but of different intensity of printing.

(D) Instead of the usual staining all over a film printed in monochrome, the dye or stain may be applied only to the blank sectionfilm and the picture itself be formed on the other section-film. When the two sections are united the eect will be similar to a stained monochrome picture.

Fig. 1 shows a double width strip of sensitized film base with two stripes of colloid each covering one half of the face area of the base, the stripe to the left being a sensitized-colloid image-forming layer and the stripe to the right being a colloid imagemodifying layer, either non-sensitized, dyed, or tinted, or sensitized with a ydifferent emulsion.

Fig. 2 shows a film with pictures in monochrome on one half and the colloid modifying-layer lefty unprinted and untinted.

Fig. 3 shows a film with a monochrome picture on the left and on the right the colloid modifying-layer dyed or tinted (for example pale blue which will give a moonlight effect to the scene when the two parts are cemented together). y

Fig. et shows a perspective diagrammatic view of the film-material.

v Fig. 5 shows a perspective diagrammatic view of the completed cinematograph film.

Manufacturing the section-)tbn material.

The thin section-film material is manufactured in the usual way by casting the waterproof cellulose upon a moving support such as a polished drum or endless belt, from which it is next removed, dried, and shrunk by the usual drying machines or drying chambers. This thin transparent cellulose support is-then prepared upon one face with a suitable adhesive substratum of the usual type, and next coated with a non-waterproof colloid layer of the desired type which is superimposed upon the cellulose support and indissolubly united thereto by the intermediate substratum, so that the finished section-film material is practically one film but of about half the thickness o f standard film. The latter is usually .O06 inch thick, but this thin section-film is only about .003 inch thick.

The superimposed colloid layer may be of gelatino-silver-bromide, or bichromated gelatine and with or without coloring matter, according to the printing process to be used, as will be hereinafter more particularly described. Where the thin section-film is only required as a cover (as i'n type A hereinbefore described) the colloid is merely plain gelatine without any sensitive salts. Although gelatine is preferred as the colloid for each of the above varieties of layers, any

other suitable colloid may be used, and for bichromate printing sh-glue, albumen, or gum are suitable.

Where it is desired to have a stronger sec- Dz'yfereat varieties of section-752m material,

and dvi/ferent printing and finishing processes required therefor.

I will now briefly describe the several variations possible in producing the film material and the print upon it.

As already indicated various sensitizing salts may be used to render the colloid layer sensitive to light, such as salts of silver, iron, uranium, alkaline bichromates, and similar well-known sensitive substances; they y,may be applied by mixing with the colloid before coating or spreading, or by process of imbibition from solutions afterwards. Suitable coloring matter such as pigments and dyes may also be incorporated when colored monochrome images are required.

Each of these different sensitizing mediums has its own advantages and disadvantages, but I prefer to utilize only the two most commonly known processes, viz those using silver salts and those using the bichromate salts, and I will now more particularly describe their application to the present invention of a scratchless monochrome film, in a variety of ways, as follows (l) For a developing-type of film using silver salts an emulsion of gelatino-silver-bromide or gelatino-silver-chloride is preferred. This is exposed, developed, fixed, washes@ and dried all in the usual well-known manner. This form of film may be printed by exposure to an electric filament lamp.

l (2) For a. developing-type of slower-printing film using silver salts, the cellulose vbase is coated with plain colloid such as gelatine or albumen, it is then passed through a bath of mixed sensitizing salts such as silver bromide, or they may be applied by separate operations from separate baths, and will be absorbed into the colloid by 'the process of imbibition. This form of film requires longer exposure, and isA then developed, fixed, washed, and dried. It may be printed by exposure to a very powerful filament lamp or preferably to a mercury lamp.

(3) For a. print-out type of film, a still slower-printing film using silver, the sensitizing salts (applied either as an emulsion or by imbibition from solution) may be silver-chloride or silver-ciltate. In this form of film the image will print-out as a visible reddish image, but requires a much longer exposure. It is next fixed, washed, and dried; but if a different color of image than this process yields is desired, the red image may be changed to sepia, purple, or warm black by `any of the usual toning processes using metallic salts. This form of film'requires printing by exposure to a mercury lamp.

(4) For a bichromate-printing type of film the cellulose support is coated with plain gelatine, fish-glue, gum, or albumen, and after drying is passed through a bath of bichromate salts; such as ammonium, potassium, or sodium bichromate. Thus the salts are absorbed by imbibition, but if preferred they may be combined with the colloid before it is coated on to the support.

When bichromate salts arey used for sensitizing the film will first require a long exposure to a mercury lamp for printing, and then developing according to the particular type of bichromate process adopted, the development vaying according to process. i

UoZored monochrome images.

(5) If a colored monochrome image is-required-such as sepia, blue, green, or the like-it may be obtained in various ways according t0 the process adopted.

For instance a plain black ima-ge, such as obtained in process l or 2, maybe changed to any of these colors by the usual metallic toning baths, or by the usual processes of dyetoning.

(6) If the film has been printed withbichromate salts, the unaltered salts are first washed away, t-he printed image then bleached, the

film dried, and next dyed in a bath of suitable dye, which by imbibition will be absorbed into the soft parts of the colloid image, and will be rejected by the hardened parts which therefore remain transparent; so that the image is formed of soft colloid dyed accord- 'ing to depths of the printing or hardening of the colloid.

If the film has been printed with silver salts, it may after development be treated in an oxydizing bath which has the effect of bleaching the black image and also rendering the colloid insoluble indirect proportion y to the action of light and amount of silver reduced; so thatafter this treatment the quickly printed silver film is similar in condition to the slowly printed bichromate filmand can be dyed in exactllythe same way. L

(For printing lms according to either of these methods (6) a positive printing clich is needed t`o give a reproduced positive.

Both of these methods give a non-relief or VAflat image, and of the type known by the technical name of Pinatype or Imbibition.

(7) In another method an image in relief, of transparent colloid, is produced and is afterwards dyed to the desired color by a suitable dye bath.

ion

Such a transparent relief image can be produced either by means of silver-sensitized or .bichromate-sensitized film, but in this case sensitive-film, which after developing in the ordinary way, must be treated to a hot-water bath until all the soluble colloid not required to form the image has been dissolved and washed away, leaving behind a transparent image of insoluble colloid in relief which is next dyed to the desired color and intensity.

(8) In still another method the coloring matter is incorporated/in the form of pigment or mordanted dye,\with the colloid matter, which in this case is preferably gelatine.

For this process a negative is required as the printing clich to yield a reproduced positive; and it is necessary that exposure be made from the back, through the transparent cellulose base, and development be effected from the front or colloid side .The resulting image, after development followed by the hot-water treatment, will be a""relief, but the coloring matter will be already in the body of the relief image and no subsequent treatment with dye baths is necessary.

This process may be worked in two ways.

For instance, if the coloring matter is incorporated with gelatino-silver-bromide emulsion, and -then treated as already described, first by exposure from the back, then developing, fixing, and hot-water treatments applied to the frontcolloid side, a relief image of the desired color is obtained direct without toning or dyeing, and with a short exposure or comparatively rapid printing, such as can be obtained by a filament lamp. This process is known by the technical name of the Carbograph process.

But if the process is worked by incorporating the coloring matter with plain gelatine, and sensitized with bichromate salts, then given a long exposure to a mercury lamp, fol-` lowed by direct development by hot water treatment only, a relief image of the desired color is obtained direct, without toning or dyeing. This process is known by the technical name of the Carbon process.

Althoughnllthe above modifications are well-known processes, some of them cannot be worked with perfectly satisfactory results upon the ordinary standard type of film now used for motion pictures; and this is particularly the case lwhere films of the ready-colored relief type are required. But with the two-piece film manufactured accordingl to this invention any or all of them can be worked with facility and each will yield excellent results.

Performing and printing.

To ensure accurate register' when finally superimposed and un1ted,^the two sect1onfilms are both perforated with identical perforations for feeding and registering` pur,-A

poses. This is done by perforating both films together by the same punch at the same stroke.

The films are printed by any suitable printing machine, either by contact or by projection, in any known way, then developed, washed, and dried by the most suitable means.

`Dauble-width film.

If desired the two sections may insteadbe made as one piece of double width. This method is preferred for many reasons, one of which is that both sections receive exactly the same treatment and therefore their expan- Sion and contractionis identical for each.

Tn such case the double-width film is perforated with two sets of perforations, by a machine having two sets of punches which perforate both sets of holes at one operation. Tf two monochrome images of different density or shades are required the two sets of images are printed simultaneously, either from a printing clich having two sets of images, or from two separate printing clichs each having a. single set of corresponding images. y L

Where the monochrome image is only printed upon one of the sections, and the other section is merely a plain cover, oneof the sections is made with plain non-sensitized colloid. This applies whether made as two single strips or as one double-width strip. In the latter case one half the width of the strip is sensitized and the other half width is not When it is preferred to form both sections of the film by means of one double-width strip of film, whichmay be considered advantageous for ease-of4 printing and assembling, such film may be formed with two side-byside sensitizings yof different character if required.

For instance one half the width may be sensitized to produce a strong, vigorous, or

mak

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even hard, short-scale image, whilst the other half is sensitized to produce a delicate, soft, long-scale image.

Or one half may to act as a covering film only.

Or one half may be sensitized to produce an image, and the other .half left unsensitized but colored with a mordanteof dye, so that when applied to the image as a dyed cover it produces the same effect as dyeing the whole of an ordinary film would produce. This is useful for moonlight and qther effects, and has the advantage that the film printer is spared the troublesome dyeing after printing, and onl needs to select beforehand a ready-dyed lmhaving one half of the desired color; and once the colored section is l be sensitized to produce y an image, and the other half left unsensitized this operation being eected. step-by-step applied it can never be scratched to leave a White line. If preferred this coloring may instead be applied tothe cellulose support itself, either to one half the double-width or to both halves.

ssemblng and uniting the two sections.

Having produced the two section-film prints as hereinbefore described, and dried them, it is now only necessary to correctly assemble and indissolubly unite them face to face in order to complete the single compound film. i The first step in this process is to apply a suitable cement to the printed faces. This may be applied before drying the film after it comes from the developing and Washing baths; or after such drying, in which case the films will require to be again dried after the cement has been applied to their faces.

The image-faces of the two films are next A"slightly moistened to render the cement sufiiciently adhesive if necessary; the two sections are next correctly assembled image-face to image-face, then adjusted and secured in accurate image-register by means of registering pins which exactly fit the holes of both lms,

and picture-by-picture; and then pressure is applied until the two kfilms become indissoluk` bly united as one.

If the two prints have been made upon one double-width strip of the same film, the llatter is longitudinally severed to form two single-Width strips after printing and finishing, then adjusted, registered, and united as described, after which its edges may be trimmed if necessary either by a slitting machine or else by milling tools.

The single-strip compound monochrome positive film is now complete.

Thus a scratchless-image, two-piece, monochrome, continuous positive film is produced at practically the same cost as the ordinary kind, but on account of the protected image being enclosed in the body of the film the completed film has a much longer life free from damage, and instead of having to be discarded before it is worn out, because its printed images are hopelessly scratched and damaged, this improved film can beV used continuously until the cellulose itself is literally worn out and becomes useless as la support.

lVhat I claim as my invention and desire to protect by Letters Patent is monochrome, cinematograph film formed from a double-width strip of film material of approximately only half standard film thickness, comprising a colored sensitized colloid layer applied to one half of the double uwidth strip to receive the image and a similarly colored non-sensitized colloid layer applied to the other half Width to give tone to the picture, both colloid layers having the same degree of expansion and contraction during treatment so that after development and printing the colored non-sensitized strip will exactly -superimpose yupon the image strip, to which it is cemented to give a positive film strip of standard width and thickness.

In testimony 'whereof I have hereunto set my hand. 'i

.TQHNEDWARD THORNTON. 

